This is an Exposure Assessment Core Facility proposal to support a grant submitted in response to the RFA entitled Centers for Children's Environmental Health and Disease Prevention Research (RFA ES-97-004). The purpose of the Exposure Assessment Core is to provide a centralized resource for the conduction of exposure assessment activities related to children's asthma research. Objectives are to provide, input into research design, field sampling equipment and support, and analytical services. Support of an Exposure Assessment Core Facility is justified based on the importance of exposure related activities associated with the cross- sectional epidemiology project, the community intervention study, and the new investigator project. In addition, the Core will interact with the Data Management Core to provide exposure assessment data for integration into epidemiologic analyses. It is expected that the Core will also interact with the basic biologic studies as they progress by helping to design more real-world exposure protocols based on the outcomes of the field based projects.